Common reference signal phase discontinuity and sequence initialization

ABSTRACT

Methods, systems, and devices are described for supporting common reference signaling in wireless communications systems. Some configurations introduce a phase discontinuity between common reference signal (CRS) transmissions on different subframes. This may address issues that may arise when a reduced CRS periodicity is utilized. Indicators may also be transmitted from base stations to user equipment (UEs) to indicate whether phase continuity may be assumed or not. Some configurations may support CRS sequence initialization. These tools and techniques may utilize an extended CRS sequence periodicity, which may increase the number of CRS sequences transmitted by a cell.

CROSS REFERENCES

The present Application for Patent is a continuation of U.S. patentapplication Ser. No. 14/162,484 by Damnjanovic et al., entitled “CommonReference Signal Phase Discontinuity and Sequence Initialization,” filedJan. 23, 2014, which claims priority to U.S. Provisional PatentApplication No. 61/757,008 by Damnjanovic et al., entitled “Methods,Systems, and Devices for Common Reference Signal Phase Discontinuity andSequence Initialization,” filed Jan. 25, 2013, each of which is assignedto the assignee hereof and expressly incorporated by reference herein.

BACKGROUND

The following relates generally to wireless communication, and morespecifically to systems, devices, and methods that utilize commonreference signals for a wireless channel for wireless communicationsystems. Wireless communications systems are widely deployed to providevarious types of communication content such as voice, video, packetdata, messaging, broadcast, and so on. These systems may bemultiple-access systems capable of supporting communication withmultiple users by sharing the available system resources (e.g., time,frequency, and power). Examples of such multiple-access systems includecode division multiple access (CDMA) systems, time-division multipleaccess (TDMA) systems, frequency-division multiple access (FDMA)systems, and orthogonal frequency-division multiple access (OFDMA)systems.

Generally, a wireless multiple-access communications system may includea number of base stations, each simultaneously supporting communicationfor multiple mobile devices. Base stations may communicate with mobiledevices on downstream and upstream links. Base stations may transmitcommon reference signals to mobile devices with specific periods.Different issues may arise when a common reference signal periodicity isreduced.

SUMMARY

The described features generally relate to one or more methods, systems,and devices for supporting common reference signaling in wirelesscommunications systems. For example, in some configurations, a phasediscontinuity may be introduced between common reference signal (CRS)transmissions on different subframes. This may address issues that mayarise when a reduced CRS periodicity may be utilized. Indicators mayalso be transmitted from base stations to user equipment (UEs) toindicate whether phase continuity may be assumed or not. Someconfigurations may support CRS sequence initialization. These tools andtechniques may utilize extended CRS sequence periodicity, which mayincrease the number of CRS sequences transmitted by a cell.

While these tools and techniques may have general applicability todifferent wireless communications systems, the methods, systems, anddevices disclosed may be utilized in particular with New Carrier Type(NCT). For example, NCT may utilize a CRS periodicity that is reduced toone subframe every 5 ms on a single antenna port. As a result,transmission from multiple physical antenna ports on a single virtualantenna port may create received signal nulls and may create CRScoverage holes. Coherent combining across different subframes may alsonot be useful in some cases, such as with high mobility user equipment(UEs). The use of phase discontinuity between CRS transmissions ondifferent subframes and/or extending a CRS sequence periodicity for CRSsequence initialization may address these issues.

In some embodiments, a method for receiving common reference signals ina wireless communications system is provided. The method may include:determining that a phase continuity may not be assumed between a firstcommon reference signal (CRS) transmission and a second CRStransmission; and/or receiving the first CRS transmission and the secondCRS transmission without maintaining the phase continuity.

Determining that the phase continuity may not be assumed between a firstCRS transmission and a second CRS transmission may include receiving anindicator that indicates that the phase continuity may not be assumed.The indicator may be received before the first CRS transmission and thesecond CRS transmission are received. Some configurations include:receiving a third CRS transmission and a fourth CRS transmission thatuse a continuous CRS phase; and/or receiving an indicator that the phasecontinuity may be assumed. In some situations, an indicator that a thirdCRS transmission and a fourth CRS transmission may be coherentlycombined may be received.

In some configurations, a phase discontinuity may occur between a firstframe and a second frame. In other examples, determining that the phasediscontinuity may not be assumed between the first CRS transmission andthe second CRS transmission may include determining the first CRStransmission and the second CRS transmission occur within a first framein some cases. The phase discontinuity may include a phase ramp up, orit may include a cycle delay diversity (CDD) that varies a CRS phase intime or in frequency. The method may be implemented in some cases withwireless communications system that uses a New Carrier Type (NCT) withrespect to the first CRS transmission and the second CRS transmission.

In some embodiments, a system for receiving common reference signals isprovided. The system may include: means for determining that a phasecontinuity may not be assumed is used between a first common referencesignal (CRS) transmission and a second CRS transmission; and/or meansfor receiving the first CRS transmission and the second CRS transmissionwithout maintaining the phase continuity.

The means for determining that the phase continuity may not be assumedbetween a first CRS transmission and a second CRS transmission mayinclude means for receiving an indicator that indicates that the phasecontinuity may not be assumed. In some configurations, the system mayinclude: means for receiving a third CRS transmission and a fourth CRStransmission that use a continuous CRS phase; and/or means for receivingan indicator that the phase continuity may be assumed. The system mayinclude means for receiving an indicator that a third CRS transmissionand a fourth CRS transmission may be coherently combined.

In some configurations, the phase discontinuity may occur between afirst frame and a second frame. In some embodiments, the means fordetermining that the phase continuity may not be assumed between thefirst CRS transmission and the second CRS transmission may include meansfor determining the first CRS transmission and the second CRStransmission may occur within a first frame. The phase discontinuity mayinclude a phase ramp up, or it may include a cycle delay diversity (CDD)that varies a CRS phase in time or in frequency. The system may use aNew Carrier Type (NCT) with respect to the first CRS transmission andthe second CRS transmission.

In some embodiments, a computer program product for wirelesscommunications systems is provided that may include a non-transitorycomputer-readable medium that may include: code for determining that aphase continuity may not be assumed between a first common referencesignal (CRS) transmission and a second CRS transmission; and/or code forreceiving the first CRS transmission and the second CRS transmissionwithout maintaining the phase continuity.

In some cases, the computer program product includes code for receivingan indicator that the phase continuity may not be assumed. The computerprogram product may also include code for receiving a third CRStransmission and a fourth CRS transmission that use a continuous CRSphase, and it may include code for receiving an indicator that the phasecontinuity may be assumed. In still further embodiments, the computerprogram product may include code for receiving an indicator that thethird CRS transmission and the fourth CRS transmission may be coherentlycombined.

A wireless communications device is provided that may include aprocessor that may be configured to: determine that a phase continuitymay not be assumed between a first common reference signal (CRS)transmission and a second CRS transmission; and/or receive the first CRStransmission and the second CRS transmission without maintaining thephase continuity.

In some embodiments of the wireless communications device, the processoris configured to receive an indicator that the phase continuity may notbe assumed. Additionally or alternatively, the processor may beconfigured to receive a third CRS transmission and a fourth CRStransmission that use a continuous CRS phase; and/or receive anindicator that the phase continuity may be assumed. In some cases, theprocessor is further configured to receive an indicator that the thirdCRS transmission and the fourth CRS transmission may be coherentlycombined. In some embodiments of the wireless communications device, thefirst CRS transmission and the second CRS transmission occur within afirst frame.

The processor of the wireless communications device may be configured todetermine that a phase discontinuity is used between a first frame and asecond frame. In some instances, the phase discontinuity includes aphase ramp up.

Further scope of the applicability of the described methods, systems,and/or devices will become apparent from the following detaileddescription, claims, and drawings. The detailed description and specificexamples are given by way of illustration only, since various changesand modifications within the spirit and scope of the description willbecome apparent to those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the presentdisclosure may be realized by reference to the following drawings. Inthe appended figures, similar components or features may have the samereference label. Further, various components of the same type may bedistinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

FIG. 1 shows a block diagram of a wireless communications system inaccordance with various embodiments;

FIG. 2 illustrates a system that can be used in accordance with thevarious embodiments;

FIG. 3 shows a block diagram of a wireless communications system with abase station and UE in accordance with various embodiments;

FIG. 4 is a block diagram illustrating a base station in accordance withvarious embodiments;

FIG. 5 is a block diagram illustrating a UE in accordance with variousembodiments;

FIG. 6 is a block diagram illustrating a base station in accordance withvarious embodiments;

FIG. 7 is a block diagram illustrating a UE in accordance with variousembodiments;

FIG. 8 is a block diagram of a MIMO communication system including aneNB and a UE in accordance with various embodiments;

FIG. 9A is a flow chart illustrating a method for wirelesscommunications in accordance with various embodiments;

FIG. 9B is a flow chart illustrating a method for wirelesscommunications in accordance with various embodiments;

FIG. 10A is a flow chart illustrating a method for wirelesscommunications in accordance with various embodiments;

FIG. 10B is a flow chart illustrating a method for wirelesscommunications in accordance with various embodiments;

FIG. 11A is a flow chart illustrating a method for wirelesscommunications in accordance with various embodiments;

FIG. 11B is a flow chart illustrating a method for wirelesscommunications in accordance with various embodiments; and

FIG. 11C is a flow chart illustrating a method for wirelesscommunications in accordance with various embodiments.

DETAILED DESCRIPTION

Methods, systems, and devices are provided for supporting commonreference signaling in wireless communications systems. For example, insome configurations, a phase discontinuity may be introduced betweencommon reference signal (CRS) transmissions on different subframes. Thismay address issues that may arise when a reduced CRS periodicity may beutilized. Indicators may also be transmitted from base stations to userequipment (UEs) to indicate whether phase continuity may be assumed ornot. Some configurations support CRS sequence initialization. Thesetools and techniques may utilize extended CRS sequence periodicity,which may increase the number of CRS sequences transmitted by a cell.

While these tools and techniques may have general applicability todifferent wireless communications systems, the methods, systems, anddevices disclosed may be utilized in particular with New Carrier Type(NCT). For example, NCT may utilize a CRS periodicity that is reduced toone subframe every 5 ms on a single antenna port. As a result,transmission from multiple physical antenna ports on a single virtualantenna port may create received signal nulls and may create CRScoverage holes. Coherent combining across different subframes may alsonot be useful in some cases, such as with high mobility user equipment(UEs). The use of phase discontinuity between CRS transmissions ondifferent subframes and/or extending a CRS sequence periodicity for CRSsequence initialization may address these issues.

The following description provides examples, and is not limiting of thescope, applicability, or configuration set forth in the claims. Changesmay be made in the function and arrangement of elements discussedwithout departing from the spirit and scope of the disclosure. Variousembodiments may omit, substitute, or add various procedures orcomponents as appropriate. For instance, the methods described may beperformed in an order different from that described, and various stepsmay be added, omitted, or combined. Also, features described withrespect to certain embodiments may be combined in other embodiments.

Referring first to FIG. 1, a diagram illustrates an example of awireless communications system 100. The system 100 includes basestations (or cells) 105, communication devices 115, and a core network130. The base stations 105 may communicate with the communicationdevices 115 under the control of a base station controller, which may bepart of the core network 130 or the base stations 105 in variousembodiments. Base stations 105 may communicate control informationand/or user data with the core network 130 through backhaul links 132.In some embodiments, the base stations 105 may communicate, eitherdirectly or indirectly, with each other over backhaul links 134, whichmay be wired or wireless communication links. The system 100 may supportoperation on multiple carriers (waveform signals of differentfrequencies). Multi-carrier transmitters may transmit modulated signalssimultaneously on the multiple carriers. For example, each communicationlink 125 may be a multi-carrier signal modulated according to variousradio technologies. Each modulated signal may be sent on a differentcarrier and may carry control information (e.g., reference signals,control channels, etc.), overhead information, data, etc.

The base stations 105 may wirelessly communicate with the devices 115via one or more base station antennas. Each of the base station 105sites may provide communication coverage for a respective geographicarea 110. In some embodiments, base stations 105 may be referred to as abase transceiver station, a radio base station, an access point, a radiotransceiver, a basic service set (BSS), an extended service set (ESS), aNodeB, an evolved NodeB (eNodeB or eNB), Home NodeB, a Home eNodeB, orsome other suitable terminology. The coverage area 110 for a basestation may be divided into sectors making up only a portion of thecoverage area. The system 100 may include base stations 105 of differenttypes (e.g., macro, micro, and/or pico base stations). There may beoverlapping coverage areas for different technologies.

In some embodiments, the system 100 may be an LTE/LTE-A network. InLTE/LTE-A networks, the terms evolved Node B (eNB) and user equipment(UE) may be generally used to describe the base stations 105 and devices115, respectively. The system 100 may be a Heterogeneous LTE/LTE-Anetwork in which different types of eNBs provide coverage for variousgeographical regions. For example, each eNB 105 may providecommunication coverage for a macro cell, a pico cell, a femto cell,and/or other types of cell. A macro cell generally covers a relativelylarge geographic area (e.g., several kilometers in radius) and may allowunrestricted access by UEs with service subscriptions with the networkprovider. A pico cell would generally cover a relatively smallergeographic area and may allow unrestricted access by UEs with servicesubscriptions with the network provider. A femto cell would alsogenerally cover a relatively small geographic area (e.g., a home) and,in addition to unrestricted access, may also provide restricted accessby UEs having an association with the femto cell (e.g., UEs in a closedsubscriber group (CSG), UEs for users in the home, and the like). An eNBfor a macro cell may be referred to as a macro eNB. An eNB for a picocell may be referred to as a pico eNB. And, an eNB for a femto cell maybe referred to as a femto eNB or a home eNB. An eNB may support one ormultiple (e.g., two, three, four, and the like) cells. In someconfigurations, an eNB 105 may introduce a phase discontinuity betweenCRS transmissions on different subframes. For example, an eNB 105 maydetermine a phase discontinuity to use between a first common referencesignal (CRS) transmission and a second CRS transmission. The eNB 105 maythen transmit the multiple common references signals, such as first CRStransmission and the second CRS transmission without maintaining phasecontinuity. This may involve utilizing the determined phasediscontinuity. In some cases, the eNB 105 may utilize a New Carrier Type(NCT) with respect to the CRS transmissions.

In some configurations, an eNB 105 may be involved with specific formsof CRS sequence initialization. For example, an eNB 105 may determine anextended common reference signal sequence period with respect to anidentified reference signal sequence period. In one example, an eNB 105may extend a CRS sequence period from 10 ms to a higher value, includingbut not limited to 40 ms or 50 ms. This may be of use, for example, withNCT. The eNB 105 may utilize the extended common reference signalsequence period in a variety of ways.

The core network 130 may communicate with the eNBs 105 via a backhaul132 (e.g., S1, etc.). The eNBs 105 may also communicate with oneanother, e.g., directly or indirectly via backhaul links 134 (e.g., X2,etc.) and/or via backhaul links 132 (e.g., through core network 130).The wireless system 100 may support synchronous or asynchronousoperation. For synchronous operation, the eNBs may have similar frametiming, and transmissions from different eNBs may be approximatelyaligned in time. For asynchronous operation, the eNBs may have differentframe timing, and transmissions from different eNBs may not be alignedin time. The techniques described herein may be used for eithersynchronous or asynchronous operations.

The UEs 115 may be dispersed throughout the wireless system 100, andeach UE may be stationary or mobile. A UE 115 may also be referred to bythose skilled in the art as a mobile station, a subscriber station, amobile unit, a subscriber unit, a wireless unit, a remote unit, a mobiledevice, a wireless device, a wireless communications device, a remotedevice, a mobile subscriber station, an access terminal, a mobileterminal, a wireless terminal, a remote terminal, a handset, a useragent, a mobile client, a client, or some other suitable terminology. AUE 115 may be a cellular phone, a personal digital assistant (PDA), awireless modem, a wireless communication device, a handheld device, atablet computer, a laptop computer, a cordless phone, a wireless localloop (WLL) station, or the like. A UE 115 may be able to communicatewith macro eNBs, pico eNBs, femto eNBs, relays, and the like. In someconfigurations, a UE 115 determines that phase continuity may not beassumed between multiple common reference signal (CRS) transmissions,such as a first CRS transmission and a second CRS transmission. In somecases, this may involve determining at the UE 115 that a phasediscontinuity is used. The UE 115 may receive multiple CRStransmissions, such as the first CRS transmission and the second CRStransmission, without maintaining the phase continuity. The UE 115 mayuse a New Carrier Type (NCT) with respect to the CRS transmissions insome configurations. In some cases, common reference signaling may bereferred to as cell-specific reference signaling.

In some configurations, a UE 115 may be utilized with respect to CRSsequence initialization. For example, a UE 115 may determine an extendedcommon reference signal sequence period with respect to an identifiedreference signal sequence period. The UE 115 may utilize the extendedcommon reference signal sequence period in a variety of ways. The UE 115may use a New Carrier Type (NCT) with respect to the CRS sequenceinitialization in some configurations.

The transmission links 125 shown in network 100 may include uplinktransmissions from a mobile device 115 to a base station 105, and/ordownlink transmissions, from a base station 105 to a mobile device 115.The downlink transmissions may also be called forward link transmissionswhile the uplink transmissions may also be called reverse linktransmissions. While the wireless system 100 is described in relation toLTE/LTE-Advanced architectures, those skilled in the art will readilyappreciate, the various concepts presented throughout this disclosuremay be extended to other types of wireless networks.

FIG. 2 illustrates a system 200 that can be used in accordance with thedisclosed embodiments. The system 200 may include a UE 115-a, which maycommunicate with an eNB 105-a (e.g., a base station, access point, etc.)using one or more component carriers 1 through N (CC₁-CC_(N)). The UE115-a and eNB 105-a may be examples of the UE 115 and eNB 105 of FIG. 1.While only one user equipment 115-a and one eNB 105-a are illustrated inFIG. 2, it will be appreciated that the system 200 may include anynumber of UEs 115 and/or eNBs 105.

In one embodiment, the eNB 105-a may transmit information to the UE115-a over forward (downlink) channels 220 and 230 on component carriersCC₁ 205 through CC_(N) 210. In addition, the UE 115-a may transmitinformation to the eNB 105-a over reverse (uplink) channels 215 and 225on component carriers CC₁ 205 though CC_(N) 210. In describing thevarious entities of FIG. 2, as well as other figures associated withsome of the disclosed embodiments, for the purposes of explanation, thenomenclature associated with a 3GPP LTE or LTE-A wireless network isused. However, it is to be appreciated that the system 200 may operatein other networks such as, but not limited to, an OFDMA wirelessnetwork, a CDMA network, a 3GPP2 CDMA2000 network and the like.

In LTE-A based systems, the UE 115-a may be configured with multiplecomponent carriers utilized by the eNB 105-a to enable a wider overalltransmission bandwidth (e.g., carrier aggregation). As illustrated inFIG. 2, the UE 115-a may be configured with “component carrier 1” 205through “component carrier N” 210, where N is an integer greater than orequal to one. While FIG. 2 depicts two component carriers, it is to beappreciated that the UE 115-a may be configured with any suitable numberof component carriers and, accordingly, the subject matter disclosedherein and the claims are not limited to two component carriers.Component carrier 205 through 210 may include respective downlinks 220and 230 as well as respective uplinks 215 and 225.

In multi-carrier operations, Downlink Control Information (DCI) messagesassociated with different UEs may be carried on a plurality of componentcarriers. For example, the DCI on a PDCCH may be included on the samecomponent carrier that is configured to be used by a UE for PDSCHtransmissions (i.e., same-carrier signaling). Alternatively, oradditionally, the DCI may be carried on a component carrier differentfrom the target component carrier used for PDSCH transmissions (e.g.,cross-carrier signaling). In some embodiments, a carrier indicator field(CIF), which may be semi-statically enabled, may be included in some orall DCI formats to facilitate the transmission of PDCCH controlsignaling from a carrier other than the target carrier for PDSCHtransmissions (cross-carrier signaling).

Enhancements to LTE/LTE-A based systems may increase the capacity andcoverage of these systems. In addition, the coordination betweendifferent cells may also improve as enhancements to LTE/LTE-A basedsystems are implemented. In one embodiment, small cell enhancementsbased on carrier aggregation may be implemented to increase the capacityand coverage of a system.

New Carrier Type (NCT) may be introduced to help optimize small cells.NCT may also be used in macro cells. In one configuration, NCT mayreduce common reference signal overhead and allow the operation ofdownlink control channels to be based on demodulation reference signals.For example, in LTE/LTE-A Rel. 12 an NCT is introduced with transmissionof cell-specific reference signals being removed in four out of fivesubframes. This may provide various performance gains for differenttransmit antenna configurations of eNBs. Reducing the CRS periodicity,however, may result in different issues. Different configurations mayaddress these issues. For example, in some configurations, phasediscontinuity between CRS transmissions on different subframes may beintroduced. In some cases, indicators transmitted from eNB 105-a to UE115-a over an NCT may indicate whether phase continuity may be assumedor not. Furthermore, with reduced CRS periodicity, there may be fewerCRS sequences transmitted by a cell. This may impact CRS sequenceinitialization. Some configurations may address this issue by utilizingan extended CRS sequence periodicity, such that the number of possiblesequences per cell may be increased (e.g., from 2 (for 10 ms CRSsequence initialization periodicity) to 8 (for 40 ms CRS sequenceinitialization periodicity)). Some configurations may also introduce CRSconfiguration information, such as time and/or frequency mapping,transmission from eNB 105-a to UE 115-a. The CRS configurationinformation may be dependent upon a system bandwidth.

FIG. 3 is a block diagram 300 illustrating a wireless communicationssystem 300 in accordance with various configurations. System 300includes a UE 115-b and a base station 105-b in accordance with variousconfigurations. The UE 115-b may be an example of the UE 115 illustratedin FIGS. 1, 2, and/or 8. The base station 105-b may be an example of thebase station illustrated in FIGS. 1, 2, and/or 8. The base station 105-bmay include a receiver module 305, a common reference signal managementmodule 310, and/or a transmitter module 315. Each of these componentsmay be in communication with each other; in some cases, these componentsmay be integrated into one or more modules. The UE 115-b may include areceiver module 355, a common reference signal processing module 360,and a transmitter module 365. Each of these components may be incommunication with each other; these components may be integrated intoone or more modules. The base station 115-b and the UE 115-b may be inwireless communication 325 with each other.

These components of the UE 115-b or the base station 105-b may,individually or collectively, be implemented with one or moreapplication-specific integrated circuits (ASICs) adapted to perform someor all of the applicable functions in hardware. Alternatively, thefunctions may be performed by one or more other processing units (orcores), on one or more integrated circuits. In other embodiments, othertypes of integrated circuits may be used (e.g., Structured/PlatformASICs, Field Programmable Gate Arrays (FPGAs), and other Semi-CustomICs), which may be programmed in any manner known in the art. Thefunctions of each unit may also be implemented, in whole or in part,with instructions embodied in a memory, formatted to be executed by oneor more general or application-specific processors.

In some configurations, the receiver module 355 of UE 115-b may includea cellular receiver and may receive transmissions from an base station105-b transmitted from transmitter module 315. The common referencesignal (CRS) management module 310 of the base station 105-b may manageCRS transmissions that may be transmitted via the transmitter module315. The CRS processing module 360 of the UE 115-b may process CRStransmission that may be received via the receiver module 355.

In some configurations, the CRS management module 310 may introduce aphase discontinuity between CRS transmissions on different subframes.For example, the CRS management module 310 may determine a phasediscontinuity to use between a first common reference signal (CRS)transmission and a second CRS transmission. The CRS management module310 and/or the transmitter module 315 may then transmit the first CRStransmission and the second CRS transmission without maintaining phasecontinuity. This may involve utilizing the determined phasediscontinuity. The UE 115-b may utilize the CRS processing module 360 todetermine that phase continuity may not be assumed between a firstcommon reference signal (CRS) transmission and a second CRStransmission. In some cases, this may involve determining that a phasediscontinuity is used. The CRS processing module 360 and/or the receivermodule 355 may receive the first CRS transmission and the second CRStransmission that use the phase discontinuity. The system 300 may use aNew Carrier Type (NCT) with respect to the CRS transmissions.

In some configurations, the CRS management module 310 of the basestation 105-b and/or the CRS processing module 360 of the UE 115-b maybe utilized with respect to CRS sequence initialization. For example,the CRS management module 310 and/or the CRS processing module 360 maydetermine an extended common reference signal sequence period withrespect to an identified reference signal sequence period. The CRSmanagement module 310 and/or the CRS processing module 360 may utilizethe extended common reference signal sequence period in a variety ofways. The wireless communications system 300 may use a New Carrier Type(NCT) with respect to the CRS sequence initialization.

Turning now to FIG. 4 and FIG. 5, FIG. 4 shows a block diagram 400illustrating a base station 105-c in accordance with variousconfigurations, while FIG. 5 shows a block diagram 500 of a UE 115-c inaccordance with various configurations. The UE 115-c may be an exampleof the UE 115 illustrated in FIGS. 1, 2, 3, and/or 8. The base station105-c may be an example of the base station illustrated in FIGS. 1, 2, 3and/or 8. The base station 105-c and the UE 115-c may be, or include,means for performing the functions described herein. The base station105-c may include a receiver module 305, a common reference signal (CRS)management module 310-a, and/or a transmitter module 315. The CRSmanagement module 310-a may include a CRS phase discontinuity module 405and/or a CRS phase state indicator module 410. The CRS management module310-a may be an example of the CRS management module 310 of FIG. 3and/or FIG. 8. Each of the components of base station 105-c may be incommunication with each other; in some cases, these components may beintegrated into one or more modules. The UE 115-c may include a receivermodule 355, a common reference signal (CRS) processing module 360-a, anda transmitter module 365. The CRS processing module 360-a may include aCRS phase state determination module 510 and/or a CRS coherent combinermodule 505. The CRS processing module 360-a may be an example of the CRSmanagement modules 360 of FIG. 3 and/or FIG. 8. Each of the componentsof UE 115-c may be in communication with each other; these componentsmay be integrated into one or more modules.

These components of the UE 115-c or the base station 105-c may,individually or collectively, be implemented with one or moreapplication-specific integrated circuits (ASICs) adapted to perform someor all of the applicable functions in hardware. Alternatively, thefunctions may be performed by one or more other processing units (orcores), on one or more integrated circuits. In other embodiments, othertypes of integrated circuits may be used (e.g., Structured/PlatformASICs, Field Programmable Gate Arrays (FPGAs), and other Semi-CustomICs), which may be programmed in any manner known in the art. Thefunctions of each unit may also be implemented, in whole or in part,with instructions embodied in a memory, formatted to be executed by oneor more general or application-specific processors.

In some configurations, the receiver module 355 of UE 115-c may includea cellular receiver and may receive transmissions from a base station,such as base station 105-c, transmitted from transmitter module 315. Thecommon reference signal (CRS) management module 310-a of the basestation 105-c may manage CRS transmissions that may be transmitted viathe transmitter module 315. The CRS processing module 360-a of the UE115-c may process CRS transmission that may be received via the receivermodule 355.

In some configurations, the CRS management module 310 may introduce aphase discontinuity between CRS transmissions on different subframes.For example, the CRS management module 310 may determine a phasediscontinuity to use between a first common reference signal (CRS)transmission and a second CRS transmission. The CRS management module310 and/or the transmitter module 315 may then transmit the first CRStransmission and the second CRS transmission without maintaining phasecontinuity. This may involve using the phase discontinuity.

Introducing phase discontinuity between CRS on different subframes maymake it such that possible signal nulls on one subframe may likely notoccur on a subsequent subframe. As a result, CRS coverage holes may beminimized as with non-coherent combining of the signal across differentsubframes probability of a coverage hole may be significantly reduced.

For UE 115-c, coherent combining may be allowed with a subframe and maybe implemented utilizing CRS coherent combiner module 505. For example,4 CRS tones per physical resource block (PRB) on two different OFDMsymbols may be utilized. Phase continuity may be maintained between twoOFDM symbols belonging to the same subframe. However, CRS on onesubframe may not be used as a reference for CRS on a subsequent subframein some cases.

The UE 115-c may utilize the CRS processing module 360-a through CRSphase state determination module 510 to determine that a phasecontinuity may not be assumed is used, for example, between a firstcommon reference signal (CRS) transmission and a second CRStransmission. This may involve determining that a phase discontinuity isused. The CRS processing module 360-a, through CRS phase statementdetermination module 510, and/or the receiver module 355 may receive thefirst CRS transmission and the second CRS transmission withoutmaintaining the phase continuity. In some cases, this may involvemultiple common references signals that use the phase discontinuity.

In some cases, the base station 105-c may indicate to a UE, such as UE115-c, whether the UE may coherently combine the signal on CRS tonesacross different subframes. Some configurations may utilize a staticindication, which may be specified by a standard. For example, it may bethat the standard configuration is for both a base station 105-c and/orUE 115-c to assume that phase discontinuity between subframes is notutilized; continuous CRS phase may be utilized in general. Signaling maybe utilized then to indicate a change from continuous CRS phase to CRSphase discontinuity mode, or vice verse. Other configurations mayutilize a semi static indication to the UE. For example, RRC signalingmay be utilized for dedicated signaling, which may be unicast, and/orthrough system information, which may broadcast in one of SIBs. Systeminformation change procedure may be invoked when phase informationchanges, for example. This information may not be expected to changefrequently, but some optimization may be utilized to access differentcell types and/or potential impact on legacy UEs that may detect andmeasure New Carrier Types (NCT), for example. As used herein, “legacyUEs” may refer to UEs configured, or optimized for operation on a systememploying single carriers and/or carrier types that pre-date NCT. Forexample, legacy UEs may be UEs configured for use on an LTE/LTE-Anetwork that predates LTE/LTE-A Rel. 12. In some implementations, forexample, if there are legacy UEs registered on the network, CRS phasediscontinuity is not used, but if there are no legacy UEs registered onthe network, CRS phase discontinuity may be used, and an indication ofCRS phase discontinuity may be signaled by the base station 105-c to theUE.

Some configurations include utilizing the CRS phase state indicatormodule 410 of base station 105-c to indicate changes in CRS phasecontinuity. For example, the CRS phase state indicator module mayindicate that it is changing from utilizing a phase discontinuitybetween CRS transmissions on different subframes to coherent phase. Insome cases, the CRS phase state indicator module may indicate that phasecontinuity may be assumed. An indicator may be received by the CRS phasestate determination module 510 of UE 115-c such that it may determinethe change and may then start coherent combining CRS signals in somecases.

In order to ensure proper UE measurements, base station 115-c maymaintain phase continuity whenever signaling indicates a change in CRSphase continuity. For example, at t_0, CRS phase may be not continuous;in this case, the UE may not coherently combine CRS signal acrosssubframes. At t_1, base station 115-c may switch to continuous CRSphase; in some cases, base station 115-c may utilize CRS phasediscontinuity module 405 to facilitate this change. At t_2, base station105-c may indicate the change in CRS phase to continuous CRS phase; itmay utilize the CRS phase state indicator module 410 to facilitate thisprocess. At t_3, a UE, such as UE 115-c may process signaling thatindicates the change and starts with coherent combining of CRS signal;UE 115-c may utilize the CRS phase state determination module 510 and/orCRS coherent combine module 505 to facilitate this process.

Base station 105-c may also indicate a change to utilize a discontinuousCRS phase utilizing CRS phase discontinuity module 405 and/or CRS phasestate indicator module 410. For example, at t_0, base station 105-c mayutilize a CRS phase that is continuous. In these cases, a UE, such as UE115-c through CRS coherent combiner module 505, may coherently combineCRS signals across subframes. At t_1, base station 105-c, through CRSphase state indicator module 410, may indicate that it is going tochange from utilizing a continuous CRS phase to utilizing adiscontinuous CRS phase. At t_2, a UE, such as UE 115-c through CRSphase state determination module 510, may process the signaling thatindicates the change and may stop with coherent combining of CRSsignals. At t 3, the base station 105-c may switch to utilize adiscontinuous CRS phase using CRS phase discontinuity module 405. Insome cases, the base station 105-c may switch to utilize a discontinuousCRS phase before it transmits an indicator to a UE indicate the CRSphase change.

In some configurations in general, base station 105-c, through CRS phasestate indicator module and/or transmitter module 315, may transmit anindicator to one or more UEs (such as UE 115-c) that indicates thatphase continuity may not be assumed. This may involve transmitting anindicator the determined phase discontinuity is to be used. Theindicator may be transmitted to the one or more UEs before the first CRStransmission and the second CRS transmission are transmitted withoutphase continuity or using the phase discontinuity.

In some cases, base station 105-c may determine that a continuous CRSphase is to be used between a third CRS transmission and a fourth CRStransmission utilizing the CRS phase state indicator module 410. Thethird CRS transmission and the fourth CRS transmission may betransmitted using the continuous CRS phase. An indicator may betransmitted utilizing the CRS phase state indicator module 410 to one ormore UE(s) that indicates that phase continuity may be assumed, or thatthe use of the determined phase discontinuity is to be discontinued.Some configurations include transmitting an indicator through CRS phasestate indicator module 410 to one or more UEs that indicates that athird CRS transmission and a fourth CRS transmission may be coherentlycombined.

On the UE side, a UE, such as UE 115-c, may be configured to receivecommon reference signals through the receiver 355 from a base station,such as base station 105-c. Utilizing the CRS phase state determinationmodule 310 in general, the UE 115-c may determine that phase continuitymay not be assumed, or that a phase discontinuity is used, between afirst common reference signal (CRS) transmission and a second CRStransmission. The UE 115-c may receive the first CRS transmission andthe second CRS transmission without maintaining phase continuityutilizing the receiver module 355 and/or the CRS phase statedetermination module 510. This may involve the use a phasediscontinuity.

In some cases, determining that phase continuity may not be assumed, orthat the phase discontinuity is used, between a first CRS transmissionand a second CRS transmission may include receiving an indicator at theCRS phase state determination module 510 that indicates that phasecontinuity may not be assumed, or that the phase discontinuity is goingto be used. In some cases, a third CRS transmission and a fourth CRStransmission may be received that use a continuous CRS phase. Anindicator may be received at the CRS phase state determination module510 that indicates phase continuity may be assumed, or that thedetermined phase discontinuity has been discontinued. In some cases, anindicator that a third CRS transmission and a fourth CRS transmissionmay be coherently combined may be received and utilized by the CRS phasestate determination module 510.

In some cases, the phase discontinuity utilized by base station 105-cmay occur between a first frame and a second frame. For example, CRS onNCT may be transmitted every 5 ms; and with a current pseudo-randomsequence for CRS generally having a 10 ms periodicity, it may bepossible to maintain CRS phase continuity within each frame, such as a10 ms (one frame) duration. Additionally or alternatively, it may be,possible to have phase discontinuity at a frame boundary or boundaries.In the case where the phase discontinuity happens between frames, a UEsuch as UE 115 may still coherently combine the CRS transmissions (e.g.,2 CRS transmissions) in one frame. In other cases, phase discontinuitymay occur between subframes of a given frame. For example, the first CRStransmission and the second CRS transmission may occur within a firstframe.

In some configurations, the base station 105-c, through CRS phasediscontinuity module 405, may introduce CRS phase discontinuity using aphase ramp up or a cycle delay diversity (CDD) process. For example,there may be CDD across antennas and variable cyclical delay in time toperturb the channel slowly over time. CDD may also be in frequency.Thus, CCD may vary a CRS phase in time or in frequency to introduce aphase discontinuity.

In some configurations, base station 105-c and/or UE 115-c may utilizeNew Carrier Type (NCT) with respect to transmitting and/or receiving CRStransmission, whether they utilize discontinuous CRS phase or continuousCRS phase.

Turning now to FIG. 6 and FIG. 7, FIG. 6 shows a block diagram 600illustrating a base station 105-d in accordance with variousconfigurations, while FIG. 7 shows a block diagram 700 of a UE 115-d inaccordance with various configurations. The UE 115-d may be an exampleof the UE 115 illustrated in FIGS. 1, 2, 3, and/or 8. The base station105-d may be an example of the base station illustrated in FIGS. 1, 2, 3and/or 8. The base station 105-d may include a receiver module 305, acommon reference signal (CRS) management module 310-b, and/or atransmitter module 315. The CRS management module 310-b may include aCRS sequence periodicity module 605 and/or a CRS configuration module610.

The CRS management module 310-b may be an example of the CRS managementmodule 310 of FIG. 3 and/or FIG. 8. Each of the components of basestation 105-d may be in communication with each other; in some cases,these components may be integrated into one or more modules. The UE115-d may include a receiver module 355, a common reference signal (CRS)processing module 360-b, and a transmitter module 365. The CRSprocessing module 360-b may include a CRS sequence boundary module 705and/or a CRS configuration determination module 710. The CRS processingmodule 360-b may be an example of the CRS management modules 360 of FIG.3 and/or FIG. 8. Each of the components of UE 115-d may be incommunication with each other; these components may be integrated intoone or more modules.

These components of the UE 115-d or the base station 105-d may,individually or collectively, be implemented with one or moreapplication-specific integrated circuits (ASICs) adapted to perform someor all of the applicable functions in hardware. Alternatively, thefunctions may be performed by one or more other processing units (orcores), on one or more integrated circuits. In other embodiments, othertypes of integrated circuits may be used (e.g., Structured/PlatformASICs, Field Programmable Gate Arrays (FPGAs), and other Semi-CustomICs), which may be programmed in any manner known in the art. Thefunctions of each unit may also be implemented, in whole or in part,with instructions embodied in a memory, formatted to be executed by oneor more general or application-specific processors.

In some configurations, the receiver module 335 of UE 115-d may includea cellular receiver and may receive transmissions from a base station,such as base station 105-d, transmitted from transmitter module 315. Thecommon reference signal (CRS) management module 310-b of the basestation 105-d may manage CRS transmissions that may be transmitted viathe transmitter module 315. The CRS processing module 360-b of the UE115-d may process CRS transmission that may be received via the receivermodule 355.

In some configurations, the CRS management module 310-b of the basestation 105-d and/or the CRS processing module 360-b of the UE 115-d maybe utilized with respect CRS sequence initialization. For example, theCRS management module 310-b and/or the CRS processing module 360-b maydetermine an extended common reference signal sequence period withrespect to an identified reference signal sequence period. The CRSmanagement module 310-b and/or the CRS processing module 360-b mayutilize the extended common reference signal sequence period in avariety of ways. The wireless communications system that base station105-d and/or UE 115-d utilize may use a New Carrier Type (NCT) withrespect to the CRS sequence initialization.

For example, CRS sequence initialization may be done with a specificperiodicity in some cases, such as with a 10ms periodicity; the same setof sequences may repeat every 10 ms, for example. For NCT, CRS has,generally, a 5 ms periodicity; and as a result, there may only be 2possible CRS sequences transmitted by a cell (instead of 10 possiblesequences as in the case when CRS may have a 1 ms periodicity). Theremay thus not be sufficient sequence randomization across cells.Measurement may thus be impacted (the impact of two or cells with badsequence correlation may impact measurement performance, for example).

The tools and techniques provided utilizing either CRS management module310-b, through CRS sequence periodicity module 605, and/or CRSprocessing module 360-b, through CRS sequence boundary module 705, mayaddress these issues through extending a CRS sequence periodicity. Forexample, with respect to NCT, the number of possible sequences per cellin NCT may be more than 2 (e.g., 40 ms (thus 8 possible sequences) or 50ms (thus 10 possible sequences)).

In order to measure neighboring cells, UE 115-d may determine thecorresponding CRS sequences used in a (sub)frame utilizing CRS sequenceboundary module 705, for example. In some general cases, to measureneighboring cells, a UE, such as UE 115-d, may detect a primarysynchronization signal (PSS) and/or a secondary synchronization signal(SSS) from which to derive a 10 ms boundary for the cell, for example,and the corresponding CRS sequences. With extended CRS sequenceinitialization, UE 115-d may (e.g., using 40 ms) detect PSS and/or SSS,followed by physical broadcast channel (PBCH) detection to determine thebeginning of a 40 ms period, and then derive CRS sequences formeasurement utilizing CRS sequence boundary module 705. In some cases,UE 115-d may detect PSS and/or SSS, and using four possible CRSsequences for measurement.

Thus, in some configurations, UE 115-d, through CRS processing module360-b and/or CRS sequence boundary module 705 in particular, maydetermine, at UE 115-d, an extended CRS sequence boundary with respectto the extended common reference signal sequence period. Determining, atthe UE 115-d, the extended CRS sequence boundary with respect to theextended common reference signal sequence period may include: detectinga primary synchronization signal (PSS), a secondary synchronizationsignal (SSS), and a physical broadcast channel (PBCH) to determine theextended CRS sequence boundary. One or more CRS sequences formeasurement may be derived after determining the extended CRS sequenceboundary. Determining, at the UE 115-d, the CRS sequence boundary withrespect to the extended common reference signal sequence period mayinclude: detecting a primary synchronization signal (PSS) or a secondarysynchronization signal (SSS); and/or utilizing multiple CRS sequencehypotheses for measurement.

In some cases, base station 105-d, through CRS management module 310-band/or CRS sequence periodicity module 605 in particular, may transmit aprimary synchronization signal (PSS), a secondary synchronization signal(SSS), and physical broadcast channel (PBCH) to facilitate one or moreUEs (e.g., UE 115-d) determining an extended CRS sequence boundary.

In some configurations, CRS sequence initialization may involve basestation 105-d determining and/or transmitting a CRS configuration to oneor more UEs (e.g., UE 115-d) utilizing CRS configuration module 610, CRSmanagement module 310-b, and/or transmitter module 315. The CRSconfiguration may depend upon a system bandwidth. In someconfigurations, UE 115-d may be configured to receive and/or determine aCRS configuration utilizing CRS configuration determination module 710,CRS processing module 360-b, and/or receiver module 355.

For example, some configurations may introduce CRS time and/or frequencymapping as a function of system bandwidth. In some cases, base station105-d may indicate this information through a physical broadcastchannel, such as an enhanced physical broadcast channel (ePBCH). Smallsystem bandwidth, for example, may have a larger number of CRSsubframes, and larger system bandwidth may have a smaller number of CRSsubframes; the CRS itself may span the entire or partial bandwidth. Insome cases, additional dependencies may be Frame Structure (FS) FS1 andFS2, and/or downlink/uplink configuration. For instance, for FS2, someconfigurations may have two DL subframes. For FS1, Multicast-BroadcastSingle Frequency Network (MBSFN) may be another factor, depending on howMBSFN may be defined, (e.g., for standalone NCT).

FIG. 8 is a block diagram of a MIMO communication system 800 includingan eNB 105-e and a UE 115-e. This system 800 may illustrate aspects ofthe system 100 of FIG. 1. The eNB 105-e may be an example of the eNB 105of FIGS. 1, 2, 3, 4, and/or 6. The UE 115-e may be an example of the UE115 of FIGS. 1, 2, 3, 5, and/or 7. The eNB 105-e may be equipped withantennas 834-a through 834-x, and the UE 115-e may be equipped withantennas 852-a through 852-n. In the system 800, the eNB 105-e may beable to send data over multiple communication links at the same time.Each communication link may be called a “layer” and the “rank” of thecommunication link may indicate the number of layers used forcommunication. For example, in a 2×2 MIMO system where eNB 105-etransmits two “layers,” the rank of the communication link between theeNB 105-e and the UE 115-e is two.

At the eNB 105-e, a transmit processor 820 may receive data from a datasource. The transmit processor 820 may process the data. The transmitprocessor 820 may also generate reference symbols, and a cell-specificreference signal. A transmit (TX) MIMO processor 830 may perform spatialprocessing (e.g., precoding) on data symbols, control symbols, and/orreference symbols, if applicable, and may provide output symbol streamsto the transmit modulators 832-a through 832-x. Each modulator 832 mayprocess a respective output symbol stream (e.g., for OFDM, etc.) toobtain an output sample stream. Each modulator 832 may further process(e.g., convert to analog, amplify, filter, and upconvert) the outputsample stream to obtain a downlink signal. In one example, downlinksignals from modulators 832-a through 832-x may be transmitted via theantennas 834-a through 834-x, respectively. A receive processor 838 mayprocess (e.g., demodulate, deinterleave, and decode) the detectedsymbols, providing decoded data for the UE 115-e to a data output, andprovide decoded control information to a processor 840, or memory 842.Processor 840 may also communicate with transmit processor 820 and/ortransmit MIMO processor 830. In some embodiments, a processor 840coupled with memory 842 may include a common reference signal managementmodule 310-c to implement the systems and methods described herein. Thecommon reference signal management module 310-c may be examples of themodule 310 of FIGS. 3, 4, and/or 6.

At the UE 115-e, the UE antennas 852-a through 852-n may receive thedownlink signals from the eNB 105-e and may provide the received signalsto the demodulators 854-a through 854-n, respectively. Each demodulator854 may condition (e.g., filter, amplify, downconvert, and digitize) arespective received signal to obtain input samples. Each demodulator 854may further process the input samples (e.g., for OFDM, etc.) to obtainreceived symbols. A MIMO detector 856 may obtain received symbols fromall the demodulators 854-a through 854-n, perform MIMO detection on thereceived symbols if applicable, and provide detected symbols. A receiveprocessor 858 may process (e.g., demodulate, deinterleave, and decode)the detected symbols, providing decoded data for the UE 115-e to a dataoutput, and provide decoded control information to a processor 880, ormemory 882. In some embodiments, the processor 880 may include a commonreference signal processing module 360-c to implement the systems andmethods described herein. The common reference signal processing module360-c may be examples of the module 360 of FIGS. 3, 5, and/or 7.

On the uplink, at the UE 115-e, a transmit processor 864 may receive andprocess data from a data source. The transmit processor 864 may alsogenerate reference symbols for a reference signal. The symbols from thetransmit processor 864 may be precoded by a transmit MIMO processor 866if applicable, further processed by the demodulators 854-a through 854-n(e.g., for SC-FDMA, etc.), and be transmitted to the eNB 105-e inaccordance with the transmission parameters received from the eNB 105-e.At the eNB 105-e, the uplink signals from the UE 115-e may be receivedby the antennas 834, processed by the demodulators 832, detected by aMIMO detector 836 if applicable, and further processed by a receiveprocessor. The receive processor 838 may provide decoded data to a dataoutput and to the processor 840. The components of the UE 115-e may,individually or collectively, be implemented with one or moreApplication Specific Integrated Circuits (ASICs) adapted to perform someor all of the applicable functions in hardware. Each of the notedmodules may be a means for performing one or more functions related tooperation of the system 800.

Similarly, the components of the eNB 105-e may, individually orcollectively, be implemented with one or more Application SpecificIntegrated Circuits (ASICs) adapted to perform some or all of theapplicable functions in hardware. Each of the noted components may be ameans for performing one or more functions related to operation of thesystem 800.

FIG. 9A is a flow chart illustrating one embodiment of a method 900-afor wireless communications. For clarity, the method 900-a is describedbelow with reference to the base stations 105 of FIGS. 1, 2, 3, 4,and/or 8. In one implementation, the common reference signal managementmodule 310 of FIGS. 3, 4, and/or 8 may execute one or more sets of codesto control the functional elements of the base station 105 to performthe functions described below.

At block 905, a phase discontinuity to use between a first commonreference signal (CRS) transmission and a second CRS transmission may bedetermined. At block 910; the first CRS transmission and the second CRStransmission may be transmitted without maintaining phase continuity. Insome cases, this may include transmitting multiple common referencesignals using phase discontinuity.

Method 900-a may also include transmitting an indicator to one or moreuser equipment (UEs) that indicates that that phase continuity cannot beassumed, such as when the determined phase discontinuity is to be used.The first indicator may be transmitted to the one or more UEs before thefirst CRS transmission and the second CRS transmission withoutmaintaining phase continuity. In some cases, this may includetransmitting multiple common reference signals using phasediscontinuity.

In some cases, it may be determined that a continuous CRS phase is to beused between a third CRS transmission and a fourth CRS transmission. Thethird CRS transmission and the fourth CRS transmission may betransmitted using the continuous CRS phase. An indicator may betransmitted to one or more user equipment (UEs) that indicates thatphase continuity may be assumed. In some cases, an indicator mayindicate that determined phase discontinuity is to be discontinued.

Some embodiments of method 900-a include transmitting an indicator toone or more user equipment (UEs) that indicates that a third CRStransmission and a fourth CRS transmission may be coherently combined.

For method 900-a, the phase discontinuity may occur between a firstframe and a second frame in some cases. The first CRS transmission andthe second CRS transmission may occur within a first frame in somecases. The phase discontinuity may be introduced using a phase ramp up.In some cases, phase discontinuity may be introduced using a cycle delaydiversity (CDD) process that may vary a CRS phase in time or infrequency.

The wireless communications system utilized for method 900-a may use aNew Carrier Type (NCT) for the first CRS transmission and the second CRStransmission.

Therefore, the method 900-a may provide for transmitting commonreference signals in a wireless communications system. It should benoted that the method 900-a is just one implementation and that theoperations of the method 900-a may be rearranged or otherwise modifiedsuch that other implementations are possible.

FIG. 9B is a flow chart illustrating one embodiment of a method 900-bfor wireless communications. For clarity, the method 900-b is describedbelow with reference to the base stations 105 of FIGS. 1, 2, 3, 4,and/or 8. In one implementation, the common reference signal managementmodule 310 of FIGS. 3, 4, and/or 8 may execute one or more sets of codesto control the functional elements of the base station 105 to performthe functions described below. Method 900-b may be an example of method900-a of FIG. 9A

At block 905-a, a phase discontinuity to use between a first commonreference signal (CRS) transmission and a second CRS transmission may bedetermined. At block 910-a; the first CRS transmission and the secondCRS transmission may be transmitted without maintaining phasecontinuity. At block 915, it may be determined that a continuous CRSphase is to be used between a third CRS transmission and a fourth CRStransmission. The third CRS transmission and the fourth CRS transmissionmay be transmitted using the continuous CRS phase at block 920. Anindicator may be transmitted to one or more user equipment (UEs) thatindicates that phase continuity may be assumed at block 925.

FIG. 10A is a flow chart illustrating one embodiment of a method 1000-afor wireless communications. For clarity, the method 1000-a is describedbelow with reference to a UE 115 of FIGS. 1, 2, 3, 5, and/or 8. In oneimplementation, the common reference signal processing module 360 ofFIGS. 3, 5, and/or 8 may execute one or more sets of codes to controlthe functional elements of the UE 115 to perform the functions describedbelow.

At block 1005, it may be determined that a phase continuity may not beassumed between a first common reference signal (CRS) transmission and asecond CRS transmission. Additionally or alternatively, it may bedetermined that a phase discontinuity is used. At block 1010, the firstCRS transmission and the second CRS transmission may be received withoutmaintaining the phase continuity. In some cases, this may involve theuse of the phase discontinuity.

Determining that the phase continuity may not be assumed between a firstCRS transmission and a second CRS transmission may include receiving anindicator that indicates that the phase continuity may not be assumed.This may involve receiving an indicator that indicates that a phasediscontinuity is to be used. In some cases, a third CRS transmission anda fourth CRS transmission may be received that use a continuous CRSphase. An indicator may be received that indicates the phase continuitymay be assumed, or that the determined phase discontinuity has beendiscontinued. Method 1000-a may also include receiving an indicator thata third CRS transmission and a fourth CRS transmission may be coherentlycombined.

For method 1000-a, the phase discontinuity may occur between a firstframe and a second frame. In some cases, the first CRS transmission andthe second CRS transmission may occur within a first frame.

The wireless communications system for method 1000-a may use a NewCarrier Type (NCT) with respect to the first CRS transmission and thesecond CRS transmission.

Therefore, the method 1000-a may provide for receiving common referencesignals in a wireless communications system. It should be noted that themethod 1000-a is just one implementation and that the operations of themethod 1000-a may be rearranged or otherwise modified such that otherimplementations are possible.

FIG. 10B is a flow chart illustrating one embodiment of a method 1000-bfor wireless communications. For clarity, the method 1000-b is describedbelow with reference to a UE 115 of FIGS. 1, 2, 3, 5, and/or 8. In oneimplementation, the common reference signal processing module 360 ofFIGS. 3, 5, and/or 8 may execute one or more sets of codes to controlthe functional elements of the UE 115 to perform the functions describedbelow. Method 1000-b may be an example of method 1000-a of FIG. 10A.

At block 1015, an indicator may be received that indicates that thephase continuity may not be assumed. This may involve receiving anindicator that indicates that a phase discontinuity is to be used. Atblock 1005-a, it may be determined that a phase continuity may not beassumed is used between a first common reference signal (CRS)transmission and a second CRS transmission; this may involve utilizingthe received indicator. In particular, a phase discontinuity may beused. At block 1010-a, the first CRS transmission and the second CRStransmission may be received without maintaining the phase continuity.In some cases, this may involve the use of the phase discontinuity. Atblock 1020, a third CRS transmission and a fourth CRS transmission maybe received that use a continuous CRS phase. At block 1025, an indicatormay be received that indicates the phase continuity may be assumed, orthat the determined phase discontinuity has been discontinued.

FIG. 11A is a flow chart illustrating one embodiment of a method 1100-afor wireless communications. For clarity, the method 1100-a is describedbelow with reference to a UE 115 of FIGS. 1, 2, 3, 7, and/or 8 or a basestation 105 of FIGS. 1, 2, 3, 6, and/or 8. In one implementation, thecommon reference signal processing module 360 of FIGS. 3, 7, and/or 8 orthe common reference signal management module 310 of FIGS. 3, 6, and/or8 may execute one or more sets of codes to control the functionalelements of the UE 115 and/or base station 105 to perform the functionsdescribed below.

At block 1105, an extended common reference signal sequence period maybe determined with respect to an identified reference signal sequenceperiod. At block 1110, the extended common reference signal sequenceperiod may be utilized. The wireless communications system of method1100-a may use a New Carrier Type (NCT) with respect to the CRS sequenceinitialization.

Method 1100-a may include determining, at a user equipment (UE), anextended CRS sequence boundary with respect to the extended commonreference signal sequence period. Determining, at the UE, the extendedCRS sequence boundary with respect to the extended common referencesignal sequence period may include: detecting a primary synchronizationsignal (PSS), a secondary synchronization signal (SSS), and physicalbroadcast channel (PBCH) to determine the extended CRS sequenceboundary. One or more CRS sequences for measurement may be derived afterdetermining the extended CRS sequence boundary.

Determining, at the UE, the CRS sequence boundary with respect to theextended common reference signal sequence period may include: detectinga primary synchronization signal (PSS) or a secondary synchronizationsignal (SSS); and/or utilizing a plurality of CRS sequence hypothesesfor measurement.

In some embodiments, method 1100-a may include receiving a CRSconfiguration at a UE. The CRS configuration may depend upon a systembandwidth.

Some embodiments of method 1100-a implemented utilizing a base stationmay include transmitting a primary synchronization signal (PSS), asecondary synchronization signal (SSS), and physical broadcast channel(PBCH) to facilitate one or more UEs determining an extended CRSsequence boundary. In some cases, a CRS configuration may be transmittedto one or more UEs. The CRS configuration may depend upon a systembandwidth.

Therefore, the method 1100-a may provide for transmitting and/orreceiving common reference signals in a wireless communications system.It should be noted that the method 1100-a is just one implementation andthat the operations of the method 1100-a may be rearranged or otherwisemodified such that other implementations are possible.

FIG. 11B is a flow chart illustrating one embodiment of a method 1100-bfor wireless communications. For clarity, the method 1100-b is describedbelow with reference to a UE 115 of FIGS. 1, 2, 3, 7, and/or 8. In oneimplementation, the common reference signal processing module 360 ofFIGS. 3, 7, and/or 8 may execute one or more sets of codes to controlthe functional elements of the UE 115 to perform the functions describedbelow. Method 1100-b may be an example of method 1100-a of FIG. 11A.

At block 1105-a, an extended common reference signal sequence period maybe determined with respect to an identified reference signal sequenceperiod. At block 1110-a, the extended common reference signal sequenceperiod may be utilized. At block 1115, an extended CRS sequence boundarymay be determined with respect to the extended common reference signalsequence period. At block 1120, one or more CRS sequences formeasurement may be derived after determining the extended CRS sequenceboundary.

FIG. 11C is a flow chart illustrating one embodiment of a method 1100-cfor wireless communications. For clarity, the method 1100-c is describedbelow with reference to a base station 105 of FIGS. 1, 2, 3, 6, and/or8. In one implementation, the common reference signal management module310 of FIGS. 3, 6, and/or 8 may execute one or more sets of codes tocontrol the functional elements of the base station 105 to perform thefunctions described below. Method 1100-c may be an example of method1100-a of FIG. 11A.

At block 1105-b, an extended common reference signal sequence period maybe determined with respect to an identified reference signal sequenceperiod. At block 1110-b, the extended common reference signal sequenceperiod may be utilized. At block 1125, a CRS configuration may betransmitted to one or more UEs. The CRS configuration may depend upon asystem bandwidth.

In additional embodiments, a method for transmitting common referencesignals in a wireless communications system is provided. The method mayinclude: determining a phase discontinuity to use between a first commonreference signal (CRS) transmission and a second CRS transmission;and/or transmitting the first CRS transmission and the second CRStransmission without maintaining a phase continuity.

Some configurations include transmitting an indicator to one or moreuser equipment (UE) that indicates that the phase continuity cannot beassumed. The indicator may be transmitted to the one or more UEs beforethe first CRS transmission and the second CRS transmission aretransmitted without maintaining the phase continuity.

In some cases, the method may include: determining a continuous CRSphase to use between a third CRS transmission and a fourth CRStransmission; transmitting the third CRS transmission and the fourth CRStransmission using the continuous CRS phase; and/or transmitting anindicator to one or more user equipment (UE) that indicates that thephase continuity may be assumed. In some situations, an indicator may betransmitted to one or more user equipment (UE) that indicates that athird CRS transmission and a fourth CRS transmission may be coherentlycombined.

In other embodiments, a method for common reference signal (CRS)sequence initialization in a wireless communications system is provided.The method may include: determining an extended common reference signalsequence period with respect to an identified reference signal sequenceperiod; and/or utilizing the extended common reference signal sequenceperiod. The wireless communications system may use a New Carrier Type(NCT) with respect to the CRS sequence initialization.

Some configurations include determining, at a user equipment (UE), anextended CRS sequence boundary with respect to the extended commonreference signal sequence period. Determining, at the UE, the extendedCRS sequence boundary with respect to the extended common referencesignal sequence period may include detecting a primary synchronizationsignal (PSS), a secondary synchronization signal (SSS), and physicalbroadcast channel (PBCH) to determine the extended CRS sequenceboundary. One or more CRS sequences for measurement may be derived afterdetermining the extended CRS sequence boundary.

In some situations, determining, at the UE, the CRS sequence boundarywith respect to the extended common reference signal sequence period mayinclude: detecting a primary synchronization signal (PSS) or a secondarysynchronization signal (SSS); and/or utilizing a plurality of CRSsequence hypotheses for measurement. Some configurations includetransmitting a primary synchronization signal (PSS), a secondarysynchronization signal (SSS), and physical broadcast channel (PBCH) tofacilitate one or more UEs determining an extended CRS sequenceboundary.

Some configurations include receiving a CRS configuration at a UE. TheCRS configuration may depend upon a system bandwidth. Someconfigurations include transmitting a CRS configuration to one or moreUEs, where the CRS configuration may depend upon a system bandwidth.

In some embodiments, a system for transmitting common reference signalsis provided. The system may include: means for determining a phasediscontinuity to use between a first common reference signal (CRS)transmission and a second CRS transmission; and/or means fortransmitting the first CRS transmission and the second CRS transmissionwithout maintaining a phase continuity.

The system may further include means for transmitting an indicator toone or more user equipment (UE) that indicates that the phase continuitycannot be assumed. The indicator may be transmitted to the one or moreUEs before the first CRS transmission and the second CRS transmissionare transmitted without maintaining the phase continuity. In some cases,the system may include: means for determining a continuous CRS phase touse between a third CRS transmission and a fourth CRS transmission;means for transmitting the third CRS transmission and the fourth CRStransmission using the continuous CRS phase; and/or means fortransmitting an indicator to one or more user equipment (UE) thatindicates that the phase continuity may be assumed. In someconfigurations, the system may include means for transmitting anindicator to one or more user equipment (UE) that indicates that a thirdCRS transmission and a fourth CRS transmission may be coherentlycombined.

For the system, the phase discontinuity may occur between a first frameand a second frame. In some cases, the first CRS transmission and thesecond CRS transmission may occur within a first frame. The phasediscontinuity may be introduced using a phase ramp up. The phasediscontinuity may be introduced using a cycle delay diversity (CDD)process that varies a CRS phase in time or in frequency. The system mayuse a New Carrier Type (NCT) for the first CRS transmission and thesecond CRS transmission.

In some embodiments, a system for common reference signal (CRS) sequenceinitialization is provided. The system may include: means fordetermining an extended common reference signal sequence period withrespect to an identified reference signal sequence period; and/or meansfor utilizing the extended common reference signal sequence period. Thesystem may a New Carrier Type (NCT) with respect to the CRS sequenceinitialization.

The system may include means for determining, at a user equipment (UE),an extended CRS sequence boundary with respect to the extended commonreference signal sequence period. The means for determining, at the UE,the extended CRS sequence boundary with respect to the extended commonreference signal sequence period may include means for detecting aprimary synchronization signal (PSS), a secondary synchronization signal(SSS), and physical broadcast channel (PBCH) to determine the extendedCRS sequence boundary. The system may further include means for derivingone or more CRS sequences for measurement after determining the extendedCRS sequence boundary. The means for determining, at the UE, the CRSsequence boundary with respect to the extended common reference signalsequence period may include: means for detecting a primarysynchronization signal (PSS) or a secondary synchronization signal(SSS); and/or utilizing multiple CRS sequence hypotheses formeasurement. Some configurations may include means for transmitting aprimary synchronization signal (PSS), a secondary synchronization signal(SSS), and physical broadcast channel (PBCH) to facilitate one or moreUEs determining an extended CRS sequence boundary.

Some configurations may include means for receiving a CRS configurationat a UE. The CRS configuration may depend upon a system bandwidth. Someconfigurations include means for transmitting a CRS configuration to oneor more UEs, where the CRS configuration may depend upon a systembandwidth.

In some embodiments, a computer program product for wirelesscommunications systems is provided that may include a non-transitorycomputer-readable medium, which may include: code for determining aphase discontinuity to use between a first common reference signal (CRS)transmission and a second CRS transmission; and/or code for transmittingthe first CRS transmission and the second CRS transmission withoutmaintaining phase continuity.

In some embodiments, a computer program product for wirelesscommunications systems is provided that may include a non-transitorycomputer-readable medium, which may include: code for determining anextended common reference signal sequence period with respect to anidentified reference signal sequence period; and/or code for utilizingthe extended common reference signal sequence period.

In some embodiments, a wireless communications device is provided thatmay include a processor that may be configured to: determine an extendedcommon reference signal sequence period with respect to an identifiedreference signal sequence period; and/or utilize the extended commonreference signal sequence period.

For some configurations, the phase discontinuity may occur between afirst frame and a second frame. The first CRS transmission and thesecond CRS transmission may occur within a first frame. The phasediscontinuity may be introduced using a phase ramp up. The phasediscontinuity may be introduced using a cycle delay diversity (CDD)process that varies a CRS phase in time or in frequency. The method maybe implemented in some cases with wireless communications system thatuses a New Carrier Type (NCT) for the first CRS transmission and thesecond CRS transmission.

The detailed description set forth above in connection with the appendeddrawings describes exemplary embodiments and does not represent the onlyembodiments that may be implemented or that are within the scope of theclaims. The detailed description includes specific details for thepurpose of providing an understanding of the described techniques. Thesetechniques, however, may be practiced without these specific details. Insome instances, well-known structures and devices are shown in blockdiagram form in order to avoid obscuring the concepts of the describedembodiments.

Techniques described herein may be used for various wirelesscommunications systems such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, andother systems. The terms “system” and “network” are often usedinterchangeably. A CDMA system may implement a radio technology such asCDMA2000, Universal Terrestrial Radio Access (UTRA), etc. CDMA2000covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releases 0 and Aare commonly referred to as CDMA2000 1X, 1X, etc. IS-856 (TIA-856) iscommonly referred to as CDMA2000 1×EV-DO, High Rate Packet Data (HRPD),etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. ATDMA system may implement a radio technology such as Global System forMobile Communications (GSM). An OFDMA system may implement a radiotechnology such as Ultra Mobile Broadband (UMB), Evolved UTRA (E-UTRA),IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM, etc.UTRA and E-UTRA are part of Universal Mobile Telecommunication System(UMTS). 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are newreleases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, andGSM are described in documents from an organization named “3rdGeneration Partnership Project” (3GPP). CDMA2000 and UMB are describedin documents from an organization named “3rd Generation PartnershipProject 2” (3GPP2). The techniques described herein may be used for thesystems and radio technologies mentioned above as well as other systemsand radio technologies. The description above, however, describes an LTEsystem for purposes of example, and LTE terminology is used in much ofthe description below, although the techniques are applicable beyond LTEapplications.

Information and signals may be represented using any of a variety ofdifferent technologies and techniques. For example, data, instructions,commands, information, signals, bits, symbols, and chips that may bereferenced throughout the above description may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. Ageneral-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, multiple microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration.

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope and spirit of the disclosure and appended claims. For example,due to the nature of software, functions described above can beimplemented using software executed by a processor, hardware, firmware,hardwiring, or combinations of any of these. Features implementingfunctions may also be physically located at various positions, includingbeing distributed such that portions of functions are implemented atdifferent physical locations. Also, as used herein, including in theclaims, “or” as used in a list of items prefaced by “at least one of”indicates a disjunctive list such that, for example, a list of “at leastone of A, B, or C” means A or B or C or AB or AC or BC or ABC (i.e., Aand B and C).

Computer-readable media includes both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. A storage medium may be anyavailable medium that can be accessed by a general purpose or specialpurpose computer. By way of example, and not limitation,computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that can be used to carry or store desiredprogram code means in the form of instructions or data structures andthat can be accessed by a general-purpose or special-purpose computer,or a general-purpose or special-purpose processor. Also, any connectionis properly termed a computer-readable medium. For example, if thesoftware is transmitted from a website, server, or other remote sourceusing a coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave, then the coaxial cable, fiber optic cable, twisted pair,DSL, or wireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,include compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above are also included within the scope ofcomputer-readable media.

The previous description of the disclosure is provided to enable aperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Throughout this disclosure the term “example” or“exemplary” indicates an example or instance and does not imply orrequire any preference for the noted example. Thus, the disclosure isnot to be limited to the examples and designs described herein but is tobe accorded the widest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method of wireless communication, comprising:transmitting an indicator that a phase discontinuity is used between afirst common reference signal (CRS) transmission and a second CRStransmission; transmitting the first CRS transmission and the second CRStransmission with the phase discontinuity between the first CRStransmission and the second CRS transmission as indicated; transmittingan indicator that a phase continuity is used between a third CRStransmission and a fourth CRS transmission; and transmitting the thirdCRS transmission and the fourth CRS transmission with the phasecontinuity between the third CRS transmission and the fourth CRStransmission as indicated.
 2. The method of claim 1, further comprising:transmitting an indicator that the third CRS transmission and the fourthCRS transmission are coherently combinable.
 3. The method of claim 1,wherein the indicator that the phase discontinuity is used istransmitted before the first CRS transmission and the second CRStransmission are transmitted.
 4. The method of claim 1, wherein thefirst CRS transmission and the second CRS transmission occur within afirst frame.
 5. The method of claim 1, wherein the phase discontinuityoccurs between a first frame and a second frame.
 6. The method of claim1, wherein the phase discontinuity comprises a phase ramp up.
 7. Themethod of claim 1, wherein the phase discontinuity comprises a cycledelay diversity (CDD) that varies a CRS phase in time or in frequency.8. The method of claim 1, further comprising: identifying a referencesignal sequence period; determining to use an extended CRS sequenceperiod with respect to the identified reference signal sequence period;and transmitting a CRS configuration associated with the extended CRSsequence period.
 9. The method of claim 8, further comprising:determining an extended CRS sequence boundary to use with respect to theextended CRS sequence period.
 10. The method of claim 1, wherein theindicator that the phase discontinuity is used comprises an indicationof a change from a continuous CRS phase mode to a discontinuous CRSphase mode.
 11. An apparatus for wireless communication, comprising:means for transmitting an indicator that a phase discontinuity is usedbetween a first common reference signal (CRS) transmission and a secondCRS transmission; means for transmitting the first CRS transmission andthe second CRS transmission with the phase discontinuity between thefirst CRS transmission and the second CRS transmission as indicated;means for transmitting an indicator that a phase continuity is usedbetween a third CRS transmission and a fourth CRS transmission; andmeans for transmitting the third CRS transmission and the fourth CRStransmission with the phase continuity between the third CRStransmission and the fourth CRS transmission as indicated.
 12. Theapparatus of claim 11, further comprising: means for transmitting anindicator that the third CRS transmission and the fourth CRStransmission are coherently combinable.
 13. The apparatus of claim 11,wherein the means for transmitting the indicator that the phasediscontinuity is used is operable to transmit before the first CRStransmission and the second CRS transmission are transmitted.
 14. Theapparatus of claim 11, wherein the first CRS transmission and the secondCRS transmission occur within a first frame.
 15. The apparatus of claim11, wherein the phase discontinuity occurs between a first frame and asecond frame.
 16. The apparatus of claim 11, wherein the phasediscontinuity comprises a phase ramp up.
 17. The apparatus of claim 11,wherein the phase discontinuity comprises a cycle delay diversity (CDD)that varies a CRS phase in time or in frequency.
 18. The apparatus ofclaim 11, further comprising: means for identifying a reference signalsequence period; means for determining to use an extended CRS sequenceperiod with respect to the identified reference signal sequence period;and means for transmitting a CRS configuration associated with theextended CRS sequence period.
 19. The apparatus of claim 11, wherein themeans for transmitting the indicator that the phase discontinuity isused comprises a means for indicating a change from a continuous CRSphase mode to a discontinuous CRS phase mode.
 20. An apparatus forwireless communication, comprising: a processor; memory in electroniccommunication with the processor; and instructions stored in the memorythat are operable, when executed by the processor, to cause theapparatus to: transmit an indicator that a phase discontinuity is usedbetween a first common reference signal (CRS) transmission and a secondCRS transmission; transmit the first CRS transmission and the second CRStransmission with the phase discontinuity between the first CRStransmission and the second CRS transmission as indicated; transmit anindicator that a phase continuity is used between a third CRStransmission and a fourth CRS transmission; and transmit the third CRStransmission and the fourth CRS transmission with the phase continuitybetween the third CRS transmission and the fourth CRS transmission asindicated.
 21. The apparatus of claim 20, wherein the instructions areexecutable by the processor to cause the apparatus to: transmit anindicator that the third CRS transmission and the fourth CRStransmission are coherently combinable.
 22. The apparatus of claim 20,wherein the instructions are executable by the processor to cause theapparatus to: transmit the indicator that the phase discontinuity isused before the first CRS transmission and the second CRS transmissionare transmitted.
 23. The apparatus of claim 20, wherein the first CRStransmission and the second CRS transmission occur within a first frame.24. The apparatus of claim 20, wherein the phase discontinuity occursbetween a first frame and a second frame.
 25. The apparatus of claim 20,wherein the phase discontinuity comprises a phase ramp up.
 26. Theapparatus of claim 20, wherein the phase discontinuity comprises a cycledelay diversity (CDD) that varies a CRS phase in time or in frequency.27. The apparatus of claim 20, wherein the instructions are executableby the processor to cause the apparatus to: identify a reference signalsequence period; determine to use an extended CRS sequence period withrespect to the identified reference signal sequence period; and transmita CRS configuration associated with the extended CRS sequence period.28. The apparatus of claim 27, wherein the instructions are executableby the processor to cause the apparatus to: determine an extended CRSsequence boundary to use with respect to the extended CRS sequenceperiod.
 29. The apparatus of claim 20, wherein the indicator that thephase discontinuity is used comprises an indication of a change from acontinuous CRS phase mode to a discontinuous CRS phase mode.
 30. Anon-transitory computer-readable medium storing code for wirelesscommunication, the code comprising instructions executable to: transmitan indicator that a phase discontinuity is used between a first commonreference signal (CRS) transmission and a second CRS transmission;transmit the first CRS transmission and the second CRS transmission withthe phase discontinuity between the first CRS transmission and thesecond CRS transmission as indicated; transmit an indicator that a phasecontinuity is used between a third CRS transmission and a fourth CRStransmission; and transmit the third CRS transmission and the fourth CRStransmission with the phase continuity between the third CRStransmission and the fourth CRS transmission as indicated.